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A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG fault and that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.
Correct answer is '1.8Ω'. Can you explain this answer?
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A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero ...
Fault current for SLG fault
Fault current for 3φ fault
Xn = 0.1 Pu
Xn (inΩ) =
Xn (inΩ) = 1.8Ω
Fault current for 3φ fault
Xn = 0.1 Pu
Xn (inΩ) =
Xn (inΩ) = 1.8Ω
Most Upvoted Answer
A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero ...
Given information:
- Voltage rating (V) of generator = 30 kV
- Frequency (f) of generator = 50 Hz
- Apparent power (S) of generator = 50 MVA
- Positive sequence reactance (X1) = 0.25 pu
- Negative sequence reactance (X2) = 0.15 pu
- Zero sequence reactance (X0) = 0.05 pu
- Fault types considered: bolted LG fault and bolted three-phase fault
- Fault current for both faults is to be equal at the generator terminal
- Grounding reactance value to be determined
Calculation steps:
1. Calculate the per-unit (pu) impedance of the generator using its apparent power and voltage rating:
Zbase = V^2 / S
Zbase = (30 kV)^2 / 50 MVA
Zbase = 18 Ω
Z1 = X1 * Zbase = 0.25 * 18 Ω = 4.5 Ω
Z2 = X2 * Zbase = 0.15 * 18 Ω = 2.7 Ω
Z0 = X0 * Zbase = 0.05 * 18 Ω = 0.9 Ω
2. Determine the fault current for a bolted LG fault at the generator terminal:
Ilg = V / Z1
Ilg = 30 kV / 4.5 Ω
Ilg = 6.67 kA
3. Determine the fault current for a bolted three-phase fault at the generator terminal:
I3φ = V / Z0
I3φ = 30 kV / 0.9 Ω
I3φ = 33.33 kA
4. Set the fault currents for both faults equal to each other and solve for the grounding reactance:
Ilg = I3φ
V / Z1 = V / Z0 + 3 * V / Zg
Zg = 3 * Z1 * Z0 / (3 * Z1 - Z0)
Zg = 3 * 4.5 Ω * 0.9 Ω / (3 * 4.5 Ω - 0.9 Ω)
Zg = 1.8 Ω (rounded to one decimal place)
5. Therefore, the value of grounding reactance in ohms is 1.8 Ω.
Conclusion:
The value of grounding reactance is calculated to be 1.8 Ω so that the fault current for a bolted LG fault and that of a bolted three-phase fault at the generator terminal are equal.
- Voltage rating (V) of generator = 30 kV
- Frequency (f) of generator = 50 Hz
- Apparent power (S) of generator = 50 MVA
- Positive sequence reactance (X1) = 0.25 pu
- Negative sequence reactance (X2) = 0.15 pu
- Zero sequence reactance (X0) = 0.05 pu
- Fault types considered: bolted LG fault and bolted three-phase fault
- Fault current for both faults is to be equal at the generator terminal
- Grounding reactance value to be determined
Calculation steps:
1. Calculate the per-unit (pu) impedance of the generator using its apparent power and voltage rating:
Zbase = V^2 / S
Zbase = (30 kV)^2 / 50 MVA
Zbase = 18 Ω
Z1 = X1 * Zbase = 0.25 * 18 Ω = 4.5 Ω
Z2 = X2 * Zbase = 0.15 * 18 Ω = 2.7 Ω
Z0 = X0 * Zbase = 0.05 * 18 Ω = 0.9 Ω
2. Determine the fault current for a bolted LG fault at the generator terminal:
Ilg = V / Z1
Ilg = 30 kV / 4.5 Ω
Ilg = 6.67 kA
3. Determine the fault current for a bolted three-phase fault at the generator terminal:
I3φ = V / Z0
I3φ = 30 kV / 0.9 Ω
I3φ = 33.33 kA
4. Set the fault currents for both faults equal to each other and solve for the grounding reactance:
Ilg = I3φ
V / Z1 = V / Z0 + 3 * V / Zg
Zg = 3 * Z1 * Z0 / (3 * Z1 - Z0)
Zg = 3 * 4.5 Ω * 0.9 Ω / (3 * 4.5 Ω - 0.9 Ω)
Zg = 1.8 Ω (rounded to one decimal place)
5. Therefore, the value of grounding reactance in ohms is 1.8 Ω.
Conclusion:
The value of grounding reactance is calculated to be 1.8 Ω so that the fault current for a bolted LG fault and that of a bolted three-phase fault at the generator terminal are equal.
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A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer?
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A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer?.
A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 30 kV, 50 Hz, 50 MVA generator has the positive, negative, and zero sequence reactances of 0.25 pu, 0.15 pu, and 0.05 pu, respectively. The neutral of the generator is grounded with a reactance so that the fault current for a bolted LG faultand that of a bolted three-phase fault at the generator terminal are equal. The value of grounding reactance in ohms (round off to one decimal place) is ___________.Correct answer is '1.8Ω'. Can you explain this answer?.
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